Voice 1
Welcome to Spotlight. I’m Christy VanArragon.
Voice 2
And I’m Joshua Leo. Spotlight uses a special method of broadcasting. It is easier for people to understand - no matter where in the world they live.
Voice 1
A beautiful orange and white clownfish swims through warm ocean water. Plants and colourful fish of all sizes fill the area. The water moves slowly, and causes the plants to slowly move with it.
Suddenly, the clownfish swims away. He hides in a safe place. No one can see him. All the other fish disappear too. The area looks empty. A predator is coming. This large fish is looking for smaller fish to eat. The small fish know this. They hide to protect themselves.
Voice 2
In another area, a different clownfish is swimming through a different area. He swims between the plants. Suddenly, all the other fish quickly swim away. The small fish hide behind rocks and in dark places. A predator is coming here too. But this clownfish does not hide. He keeps swimming around the reef. He does not know that the predator is there.
Voice 1
What is the difference between these two clownfish? Why did one clownfish swim to safety? Why did the other fish not protect itself?
Voice 2
Today’s Spotlight is on clownfish. Ocean waters are changing all around the world. These changes are causing problems for clownfish. Today we will discuss those changes and how they affect these beautiful fish.
Voice 1
Clownfish live in warm ocean water. They live in reefs. Reefs look like hard, thin rocks. But they are actually made by small animals called coral. Reefs are full of animals and fish. Clownfish live with anemones in these reefs. Anemones are unusual animals. They look like plants. And they are usually very dangerous to other fish. They sting and kill small fish for food.
Voice 2
However, clownfish have a relationship with anemones. Anemones need clownfish to clean them. Clownfish eat small insects that live on anemones. And the clownfish need the anemone for protection. A clownfish can hide inside the anemone if a predator is coming.
Voice 1
However, recently scientists have noticed something strange. Some clownfish are not hiding from predators in the anemones. Instead, like the clownfish we described above, these clownfish do not seem to notice the predators. Scientists who study clownfish do not understand this new behaviour. But they believe the problem may be the rising levels of carbon dioxide in the oceans.
Voice 2
The climate on the earth is changing. One big change is more carbon dioxide gas in the air. This carbon dioxide comes from many things. Factories, cars, farms, and fires pollute the air with carbon dioxide. There are some ways that people are working to solve this problem. But even with this work, carbon dioxide levels continue to rise.
Voice 1
Most importantly, the world’s climate is getting warmer. This causes more extreme weather around the world. But it also affects the world’s oceans. It makes the water warmer, but it also makes the water more acid. This change has terrible effects on the animals and plants. It kills the small coral animals that build the reef. And it causes behaviour changes in many animals. For clownfish it may mean a more dangerous life.
Voice 2
Dr. Steve Simpson is a scientist at Bristol University. He was worried about these clownfish. So he did an experiment to study clownfish. He and other scientists set up different tanks of water. There was only one difference between the tanks. Each tank had a different level of carbon dioxide. One tank had normal water from the ocean. The other tanks had water with higher levels of carbon dioxide.
Voice 1
The scientists put clownfish in the different tanks. Then they played the sounds of predators. Most of the clownfish in the tank with normal water swam into hiding. Only a small number did not swim away from the predators.
Voice 2
But most of the clownfish in the tanks with high carbon dioxide did not hide. These carbon dioxide levels are the levels that scientists expect in the world’s oceans in the future. Scientists believe that these clownfish cannot sense predators. They believe these clownfish are not able to hear or smell a predator coming. The clownfish are losing their senses. Dr Simpson described the possible effects of this loss with the BBC. He said,
Voice 3
“Sounds are also important for finding a mate, hunting in groups and finding food. So if any of those abilities are gone, it would be a very lost fish.”
Voice 2
He added that it would also make things easier for predators,
Voice 3
“The reef can like a ‘wall of mouths’ waiting to receive the clownfish.”
Voice 1
Clownfish are already experiencing the effects of carbon dioxide in the ocean. At this time, only some clownfish show signs of the problem. But in the future, carbon dioxide levels may rise more. And this could affect many more clownfish.
Scientists do not know exactly how the carbon dioxide is affecting the fish. Scientists could find no physical damage to the fishes’ ears. They believe the gas could be affecting the fishes’ nerves or stress levels instead. They will perform more experiments in the future to answer these questions.
Voice 2
However, scientists think the carbon dioxide causes a neurological change in the fish. This change to the brain could completely destroy the clownfish. But some scientists still believe that clownfish will change to accept the new environment. This can only happen if the change to the ocean water is very slow - over many decades. The clownfish may learn new ways to notice predators. Or, their senses may not be as greatly affected.
Voice 1
It is clear that unless carbon dioxide levels around the world drop, many changes will happen to the ocean. The change to the clownfish is just one small sign of larger changes to the ocean environment. The clownfish live in beautiful coral reefs. But growing ocean acidity is killing the small coral animals. Without coral, the reefs begin to break. Already, reefs in many places are dead - no animals or plants live in them.
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